lcd: mpc823: move mpc823-specific lcd_logo_set_cmap code to mpc8xx_lcd.c

Reduce the bitmap_plot #ifdef complexity by extracting MPC823-specific code for
setting cmap into its own implementation of lcd_logo_set_cmap(), implemented in
mpc8xx_lcd.c. In the MPC823 implementation, ARRAY_SIZE(bmp_logo_palette) is
switched for BMP_LOGO_COLORS to avoid having to include bmp_logo_data.h, which
would cause a compilation error because the logo data and palette arrays would
be defined twice.

This is a step towards cleaning bitmap_plot() of platform-specific code.

Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Bo Shen <voice.shen@atmel.com>
Tested-by: Josh Wu <josh.wu@atmel.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Anatolij Gustschin <agust@denx.de>